1. Field of the Invention
The present invention relates to an inorganic fiber catalyst, a production method thereof and a catalyst structure. More specifically, the present invention relates to an inorganic fiber catalyst that contains catalyst component particles which are microfabricated and highly dispersed, and is capable of suppressing exfoliation of the catalyst component particles, and relates to a production method of the inorganic fiber catalyst, and a catalyst structure using the inorganic fiber catalyst.
2. Description of the Related Art
In recent years, a diesel engine has attracted attention since the diesel engine has better fuel efficiency than a gasoline engine and is capable of reducing an emission amount of carbon dioxide (CO2). In such a diesel engine, reduction of particulate matter (PM) contained in exhaust gas has become a technical subject. For this technical subject, there has been employed a method of collecting and purifying the PM by using a diesel particulate filter composed of an inorganic fiber on which a catalyst is supported.
Moreover, in some case, the PM cannot be oxidized sufficiently at a temperature of the exhaust gas discharged by the diesel engine, and accordingly, it has been examined to also use a promoter. For example, it has been reported that a rare earth element oxide such as cerium-praseodymium oxide and cerium-zirconium oxide is effective in oxidizing the PM (refer to Koichiro HARADA, Yoshinori TSUSHIO, and Akihide TAKAMI, Journal of the Japan Petroleum Institute, Vol. 48, No. 4, p. 216 (2005).
Meanwhile, as a method of supporting the catalyst component and the promoter component on such the inorganic fiber, there has been known a method of dipping the inorganic fiber into an aqueous solution containing a surfactant and organic acid salts of these components, followed by drying/baking (refer to Japanese Patent Unexamined Publication No. 2002-326036).